A spindle unit used for a miniature motor or miniature rotor has been conventionally formed as shown in FIG. 22.
That is to say, a pair of radial ball bearings 21 and 22 are arranged in the upper and lower parts of the outer periphery of a shaft 20, a cylindrical spacer 23 is arranged between the outer races 21a and 22a of these radial ball bearings 21 and 22 to position the radial ball bearings 21 and 22 with respect to each other, these are fixed within the bore H of a bearing housing 24, a rotor 25 such as a pulley, disc or turntable is fixed to the end of the shaft 20 and the shaft 20 is rotated from the other end.
The rotary mechanism of a conventional tape guide roller has been formed substantially the same.
However, in the above mentioned construction, in order to prevent dust or the like from entering the radial ball bearings 21 and 22 and reducing the performance, a so-called double sealing structure is used in which sealing members S are arranged on both sides of balls 21c or 22c within each of the radial ball bearings 21 and 22.
This construction has the disadvantage that the radial ball bearings 21 and 22 have many component parts, are complicated to assemble and are high in cost. Also, because of the clearances (in four places) of the radial ball bearings 21 and 22 the shaft 20 can tilt during rotation.